WS3B Dual Trace Oscilloscope pattern

    In engine management and control, there are sensors which sense both inputs and outputs of an engine. The inputs determine the requiring outcomes for the outputs, and there are output sensors to feedback, bringing a close-loop system. This makes almost every sensible components on an engine manageable, and thus everything seems to almost affect the operation of one another.
   The dual trace function on the multipurpose oscilloscope is to allow us to see relationships between different sensors. This way we can understand how responsive engine's subsystems are through the ECM's management.
Also, this confirms, and enhances our knowledge about engine's management system as well as each component's operation.

MAP(analogue) vs Injector

Description:
Map only increases for a momentary amount of acceleration, then drops down low.
Injector pulse width increases as the acceleration takes place, then decreases when the engine speed stables.
MAP and Injector are not timed actuators, but sequentially affecting each other.

Relationship:
When Map signal is high, the ECU knows there is more air coming in, hence increases the short term fuel trim(STFT) - pulse width of the injector to give more fuel. If the throttle is kept wide open, the pulse width will be kept @ high level or increasing to match the air's demand for more fuel. Fuel/sec means more Force/second, means how low the acceleration will take place.
If the throttle is kept @ a level, the pressure in MAP will be overwhelmed by rapid vacuum from the intake stroke, dropping the MAP signal down, hence the ECU knows that there is no need for more acceleration, so just keep the Injector's pulse width at a level to stabilize the RPM.

How do they affect each other?
MAP is a sensor, an input, Injector is an actuator controlled by ECU using MAP as a command reference. MAP voltage affects how much fuel is given in. Injector doesn't affect atmospheric pressure, hence it doesn't affect MAP sensor. E.G: Map's vacuum feed hose is leaking, the MAP voltage is always high, then ECU will try to give more and more fuel=> Injector's pulse width is high.


RPM vs Injector

Description:
RPM: sine waves, identical, frequency represents how fast is engine's RPM. At idle, waves are long and less frequent, at high speed, waves are bigger in amplitude, shorter in length, higher frequency.
Injector: short pulse width @ idle, longer pulse width when accelerating, that means when there is a change of speed, not how fast the engine speed.
Not timed sensor and actuator but naturally affect each other.

Relationship:
RPM aka Crank sensor or CAM sensor, is the actuator's output sensor. It is also an input in term of feed back for various management systems like ABS, ESP, Traction control etc...Engine speed is linked to 2 power source: External force exerts on vehicle's drive and the engine power itself. For example, a car down slope can accelerate using gravity without the engine running. Force creates acceleration. In term of injector, giving more fuel means burning more fuel, thus means power, hence force.
The injector pulse width decides the amount of acceleration for the RPM, but RPM doesn't affect Injector pulse width, even if its faulty. This is virtually right, but technically, in some advance engine management module, RPM can be a reference in association with other sensor to make the ECM cut down on fuel.


Oxygen sensor vs Injector

Description:
O2 sensor: slow, low cross counts data, some time intermittent=> old and sluggish. Signal oscillates from 0.1 to 0.9, more frequent at idle, less frequent and more often at higher voltage when accelerating and high RPM.
Low voltage indicating lean mixture, high means rich mixture.
Injector: small pulse width @ idle, big pulse width @ acceleration, smaller pulse width @ high stable RPM but opens more frequently.
Not timed sensor and actuator but naturally affect each other.

Relationship:
Burning more fuel affects another outcome, that is emission. The O2 sensor will be more likely to spend more time in the 0.9V when either injector pulse width is wide or @ high RPM, because high RPM means more frequent pulse width, thus more fuel anyway. But in reverse, a malfunction O2 sensor wouldn't virtually affect the injector. Unless it is emission control function in the ECU that tells the injector to cut down on fuel when idling with a leaner mixture, all thanks to the O2 sensor.


Ignition primary vs Injector

Description:

Both happen as frequent as RPM.
Neither is INJ voltage nor IGp voltage affect each other voltage.
Injector's pulse width doesn't affect Ignition dwell time, or firing voltage. As speed increases, injector pulse width gets big for a moment then go low but more frequent=> more fuel/ second anyway.
Ignition spark is critically affected by RPM, not the amount of acceleration, the faster the speed, the more advanced the dwell angle, but that doesn't mean more dwell time overall. Less dwell time and firing voltage @ higher speed.
Not timed actuators. But INJ affect RPM, and RPM affect Ignition timing.

Virtually, when any part of the Ignition system is faulty, a spark can't be delivered or misfire, the engine loses its power. When Injector is clogged can't deliver fuel, there is not enough fuel to ignite, then engine loses its power also.